The Marsh Builders最新文献

{"title":"The Microbe Solution","authors":"S. Levy","doi":"10.1093/oso/9780190246402.003.0007","DOIUrl":"https://doi.org/10.1093/oso/9780190246402.003.0007","url":null,"abstract":"In the hot, dry summer of 1858, the Thames was a stew of sewage that festered in the sun, giving off an unbearable stench. “We believe this to be the uncleanest, foulest river in the known world,” wrote a London pundit in July. “There you shall see in the brief space of half an hour and two or three miles, a hundred sewers disgorging solid filth, a hundred broad acres of unnatural, slimy chymical compost . . . The water—the liquid rather—is inky black.” Dockworkers suffered nausea, headache, sore throats, temporary blindness—some of them fainted from breathing in the river’s aroma. In the newly rebuilt Houses of Parliament, on the riverbank, legislators choked on what the press labeled “the Great Stink.” The Thames had been badly polluted for decades, but the heat and low water that summer brought the situation to a crisis. Benjamin Disraeli, leader of the House, held a handkerchief over his nose as he fled from the Chamber, complaining that the Thames had become a “Stygian Pool.” In July 1858, he introduced a law that authorized the construction of a costly new sewer system, designed by engineer Joseph Bazalgette, that would carry London’s waste downstream of the city. Britain’s rivers were overwhelmed with sewage, its cities bursting at the seams. Between 1801 and 1841 London’s population had grown from 958,000 to 1,948,000. Numbers of people living in smaller cities like Leeds, Bradford, and Huddersfield doubled or tripled in the same span of time. While the same pattern held in other European and American cities, geography made the problem more intense in Britain, where the rivers were too small to carry off the wastes of the towns that sprouted on their banks. In 1885, engineer James Gordon estimated that dumping the raw sewage of the major towns along the Rhine would give that river a concentration of only one part sewage per 2,345 parts water. The lower Lea, a tributary of the Thames whose upstream flows had been diverted to provide drinking water for London, was by contrast composed of two- thirds sewage.","PeriodicalId":133667,"journal":{"name":"The Marsh Builders","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130606158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Tide Rises","authors":"S. Levy","doi":"10.1093/oso/9780190246402.003.0017","DOIUrl":"https://doi.org/10.1093/oso/9780190246402.003.0017","url":null,"abstract":"David Sedlak, an environmental engineering professor at the University of California– Berkeley, stands on a levee near San Francisco Bay’s eastern shore. Manmade embankments extend for many miles, lining much of the bay’s edge, but Sedlak, a lean, intense guy, is fired up about this newly built one. Instead of the usual barren concrete, the bayward face of the levee slopes gently beneath a dense growth of native wetland plants. From muddy clumps of roots and rhizomes placed here only a year ago, the plants have sprouted into a lush palette of green, from the deep dark of Baltic rush to the bright tones of creeping wild rye. Sedlak is part of a bold experiment. If it succeeds, the project may reshape the East Bay shoreline, restoring a vast acreage of lost tidal wetlands that will be nourished by treated wastewater. The hope is that vegetated levees (the official moniker for the concept is the Horizontal Levee) will save money and energy, recycle treated sewage to create habitat, and help the urbanized East Bay adapt to rising sea levels. Conventional levees form steep concrete or earthen walls that armor roads and buildings against the bay’s powerful waves. The Horizontal Levee is a lovely contrast, a compressed version of a natural habitat long missing from the shoreline. The transition zones, or ecotones, between land and bay were biologically rich places that once hosted a diversity of native plants and animals. Since the Bay Area was settled, wetlands have been diked off from both the open bay and the surrounding land. Between 1800 and 1998, 92 percent of tidal marshes were lost to diking and filling. “In San Francisco Bay, we’ve separated the contacts between the terrestrial and the tidal,” explains Peter Baye, a consulting ecologist whose deep knowledge of remnant natural wetlands acts as guideline for the creation of the Horizontal Levee. Habitats that once formed a continuous gradient from dry land to salt marsh have been boxed off, separated by dikes. The disappearance of what ecologists call the “back end” of tidal marshes has been a significant loss.","PeriodicalId":133667,"journal":{"name":"The Marsh Builders","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121125336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cholera’s Frontiers","authors":"Sharon Levy","doi":"10.1093/oso/9780190246402.003.0005","DOIUrl":"https://doi.org/10.1093/oso/9780190246402.003.0005","url":null,"abstract":"Sewage as we know it—the everyday miracle of feces disappearing down the toilet, pushed by a never-ending flow of clean water—is a recent invention. The flush toilet itself has been created, and then forgotten, many times down through the ages. But the grand scheme that we all take for granted—an endless supply of clean water piped in and limitless amounts of dirty water piped out—was thought up by Edwin Chadwick, a British lawyer turned public health crusader, in the 1840s. Back then the cities of the Old World were awash in human waste. Even the most elegant homes had privies that emptied into cesspits, where decades of accumulated filth sat rotting beneath the parlor floor. The poor lived in tenements where dozens of people might have to share one privy. Chadwick supervised a survey of sanitary conditions in English cities that came up with some amazing statistics. In parts of Manchester there was one privy to every 215 people. Some houses had yards covered six inches deep in “human ordure,” which the inhabitants crossed by stepping on bricks. “Sir Henry De La Beche was obliged at Bristol to stand up at the end of alleys and vomit while Dr. Playfair was investigating overflowing privies,” Chadwick wrote of one of his colleagues. “Sir Henry was obliged to give it up.” London had sewers, of a sort: They were open ditches that sloped toward the Thames, and were meant to drain stormwater out of the streets. But by Chadwick’s day, the gunk from thousands of overflowing cesspits emptied into these sewers, then oozed its way into the river. Parliament’s windows on the riverfront had not been opened in years because of the stench. The Chelsea Water Company, which provided drinking water to many Londoners, still had its intake a few feet from the outfall of the Ranelagh sewer. An editorial in The Spectator pointed out that city residents paid the water companies “340,000 pounds per annum for a more or less concentrated solution of native guano.”","PeriodicalId":133667,"journal":{"name":"The Marsh Builders","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132903652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fighting the Big Sewage Machine","authors":"S. Levy","doi":"10.1093/oso/9780190246402.003.0010","DOIUrl":"https://doi.org/10.1093/oso/9780190246402.003.0010","url":null,"abstract":"Salmon were George Allen’s passion. He spent his professional life seeking to combine salmon restoration with sewage recycling, a mission as daunting as the upstream struggle of a weary chinook blocked by a dam. Salmon begin their lives as eggs buried in a gravel nest on a stream bottom, from which tiny fish emerge, swim to the surface, and start to feed. The young grow, lose their infant stripes, and swim to sea, steered by instinct and a physical drive to reach salt water. They range through the ocean for two years or more, growing into magnificent creatures. When the time is right, they return to their home streams to spawn. Crowds of wild, abundant salmon once fought their way up the rivers of the Pacific coast from central California to Alaska. The cycle was eternal, with no distinct beginning or end, until white civilization blocked the rivers with dams and smothered the spawning grounds in silt. By the time Allen came to teach fisheries at Humboldt State, in 1957, salmon runs all along the west coast were depleted. Most of the ancient stocks that had once populated the streams feeding Humboldt Bay were extinct. In an obscure corner of Arcata’s treatment plant, Allen and his students raised young coho and chinook in treated sewage flowing out of the city’s oxidation ponds. Soon after he arrived in Humboldt, Allen had begun planning to resurrect the bay’s lost salmon stocks, and Arcata’s sewage oxidation ponds proved the only likely spot to launch his quest. The oxidation ponds were a constant source of fresh water, with access to a stream, Jolly Giant Creek, which formed a small estuary where he could release fish to the bay. He took fingerlings from any hatchery that had extras and raised them to the moment of smoltification, when they lost their baby stripes, turned shiny silver, and transformed from freshwater to saltwater creatures. His intense hope was that they’d go to sea and return as adults, making the city’s wastewater plant the center of a salmon revival in Humboldt Bay.","PeriodicalId":133667,"journal":{"name":"The Marsh Builders","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115540367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strangled Waters: First Wave","authors":"S. Levy","doi":"10.1093/oso/9780190246402.003.0009","DOIUrl":"https://doi.org/10.1093/oso/9780190246402.003.0009","url":null,"abstract":"On a balmy day in June 1955, George Anderson took his sailboat out on Lake Washington, the long stretch of fresh water that separates Seattle from its eastern suburbs. Anderson had recently finished his doctoral research on phytoplankton, and knew the lake well. The water that day looked odd; he noticed a strange brown tinge. So he collected a sample in an empty beer bottle and brought it back to the University of Washington lab where he worked with his mentor, W.T. Edmondson, the ranking authority on the lake. Under the microscope, Anderson and Edmondson found a life form they’d never seen before. It grew in long, narrow chains, striated with lines that separated one cell from the next. They thought this might be a species infamous among limnologists, the cyanobacterium Oscillatoria rubescens. (Cyanobacteria, popularly known as blue-green algae, are in fact distinct from and far more ancient than algae. They appeared more than 3 billion years ago, when the planet was inhabited only by microbes, and were the first organisms to evolve photosynthesis. Their proliferation and release of great volumes of oxygen profoundly changed the chemical makeup of Earth’s atmosphere, making the evolution of complex life possible.) The researchers needed to be sure, so they sent a sample off to an expert, who confirmed their suspicions. O. rubescens signaled deteriorating conditions in Lake Washington. To Edmondson, it also meant an unprecedented opportunity to track the impacts of nutrient overload. O. rubescens had been the harbinger of drastic change in a number of western European lakes. The best-known case was that of Lake Zurich in Switzerland. Fed by Alpine glaciers, Lake Zurich was, until the late 1800s, an expanse of blue known for its abundant populations of whitefish and lake trout, which thrive in deep water. The lake is made up of two basins separated by a narrow passage. In the late nineteenth century towns at the edge of the lower basin, the Untersee, abandoned privies for flush toilets, and began to release their raw sewage into the lake.","PeriodicalId":133667,"journal":{"name":"The Marsh Builders","volume":"982 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116218897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Wild Things","authors":"S. Levy","doi":"10.1093/oso/9780190246402.003.0015","DOIUrl":"https://doi.org/10.1093/oso/9780190246402.003.0015","url":null,"abstract":"A group of sea otters laze at the edge of Elkhorn Slough. They float on their backs in the steel- gray water, paws folded against their chests, gazing at the small boat steered by ecologist Brent Hughes of the University of California– Santa Cruz. Hughes has documented a profound shift in the slough’s ecology, triggered by the otters. Sea otters were nearly driven to extinction by fur hunters in the 1800s, and were gone from Elkhorn Slough for a century. In 1984, when the first sea otters recolonized, Elkhorn Slough’s once bountiful eelgrass beds had dwindled to a few small, scattered patches. Now, more than thirty years after the sea otters’ return, expanding eelgrass beds grow lush beneath the water’s surface, the dense leaves sheltering juvenile fish and feeding an array of invertebrate grazers. The slough, on the central California coast, is one of the most severely polluted estuaries on the planet. Artificial fertilizer applied to 2.69 million acres of farmland in the neighboring Salinas Valley runs into its waters. The excess nutrient load causes eutrophication. It also fuels the growth of epiphytic algae that thrive on the surface of eelgrass leaves, blocking the sunlight the grass needs and smothering whole beds. The problem is common in estuaries around the globe, which receive heavy loads of nutrients from rivers draining polluted watersheds. Seagrass meadows filter contaminants from water and prevent coastal erosion in addition to acting as nurseries for fish and invertebrates. These crucial habitats are disappearing. The global distribution of seagrasses has decreased by 29 percent over the last 140 years, and 58 percent of the surviving seagrass meadows are in decline. Nutrient pollution of coastal waters had long been thought to be the main driver of this trend. But in Elkhorn Slough, the eelgrass has made a remarkable comeback even as pollution loads continued to climb. The mechanism of this welcome ecological shift was unknown until Hughes demonstrated that sea otters are the key. He began to put the pieces of the puzzle together when he went diving in Tomales Bay, an unpolluted estuary to the north. The eelgrass in Elkhorn Slough was lush and green despite intense pollution; in Tomales Bay, where there are no sea otters, the eelgrass was a dull brown, smothering under epiphytic algae.","PeriodicalId":133667,"journal":{"name":"The Marsh Builders","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122887983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strangled Waters: Second Wave","authors":"S. Levy","doi":"10.1093/oso/9780190246402.003.0014","DOIUrl":"https://doi.org/10.1093/oso/9780190246402.003.0014","url":null,"abstract":"In August 2014, the water supply for the city of Toledo, Ohio, was poisoned. Officials issued an order to the half- million residents connected to the municipal water supply: Don’t drink, cook, or brush your teeth with the water. Do not use it to bathe your children, and don’t give it to your pets. Stores ran out of bottled water, and residents had to wait in long lines or travel to neighboring towns to find more. The culprit was a bright green plume of Microcystis, a cyanobacterium that thrives in warm water tainted with heavy loads of phosphorus and nitrogen. Every spring, rains wash a pulse of nutrients off fertilized fields and send it down the Maumee and Sandusky rivers and into western Lake Erie. Every summer, as water temperatures rise, Microcystis forms an iridescent mat over parts of the lake’s surface. In early August 2014, strong winds blew a lawn of cyanobacteria over Toledo’s water intake, which lies just outside the Maumee’s mouth. Tests showed that the city’s water contained dangerous levels of microcystin, a liver toxin produced by the bloom. The drinking water crisis was a dramatic signal of Lake Erie’s descent back into eutrophication. In the 1980s, after sewage plants in the watershed were upgraded and phosphate detergents banned, Lake Erie experienced a revival. Algal blooms faded, and populations of walleye rebounded. The lake grew a thriving tourist industry based on sport fishing. Then, in 1995, researchers recorded the lake’s first wide­spread bloom of Microcystis. Eruptions of Microcystis have since become a predictable event striking the western Lake Erie basin every summer. The most widespread and long- lasting blooms hit in 2011 and 2015, after intense spring rains dumped heavy loads of nutrients into the lake. Climate models forecast warmer summer temperatures and heavier spring rains for the Great Lakes region. Those conditions are a recipe for more and larger algal blooms, and are likely to favor Microcystis in particular. The regulatory efforts of the 1970s and 1980s made great progress in cleaning up discharges from industries and sewage treatment plants, but failed to address nonpoint source pollution flowing from farm fields and city streets.","PeriodicalId":133667,"journal":{"name":"The Marsh Builders","volume":"154 8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125885440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revolution","authors":"S. Levy","doi":"10.1093/oso/9780190246402.003.0012","DOIUrl":"https://doi.org/10.1093/oso/9780190246402.003.0012","url":null,"abstract":"The fight over the Humboldt Bay Wastewater Authority (HBWA) project had turned bitter and personal. HBWA’s attorney, John Stokes, and most of its board members had lobbied hard against Arcata’s alternative treatment plan. Dan Hauser, usually diplomatic, seethed with resentment. “HBWA has set itself up as the enemy,” he wrote in a September 1977 opinion piece in the Arcata Union. “Therefore, we have no alternative but to defend ourselves by attacking HBWA . . . We must stop this $52 million boondoggle.” Hauser, still Arcata’s representative on the HBWA board, pledged to work toward the “total redesign or total destruction” of the regional sewage system. Other members of HBWA were growing panicky. The Committee for a Sewer Referendum’s lawsuit kept the board from issuing bonds to finance construction, while inflation caused the project’s already huge price tag to balloon. Concealing the move from Hauser, the board applied for a $5.9 million loan from the US Environmental Protection Agency (EPA). Arcata, at Mayor Hauser’s suggestion, promptly sued HBWA for seeking the loan without the city’s consent. Meanwhile, Hauser organized an appeal for Arcata’s wetland treatment system before the State Water Resources Control Board. The city mustered support from representatives of the US Fish and Wildlife Service and Audubon Society, along with academic experts on Humboldt Bay oysters and low-tech sewage treatment. Wade Rose, the shaggy upstart from the governor’s Office of Appropriate Technology, would speak. After Stokes cross-examined Rose at the regional board hearing, “it became a crusade for the entire Office of Appropriate Technology,” Hauser explains. “They singled out HBWA as the ultimate in obsolete technology and concrete overkill.” When the Arcata contingent arrived at the state board hearing in Sacramento, one of the board members, brandishing a newspaper clipping in his hand, called Hauser forward. The clipping was a story from the Arcata Union, quoting Hauser saying that the marsh project would not get a fair hearing. “He asked why I was there if I believed they were already biased against me,” Hauser remembers. “I told him we have to go through this process to get to the next step.”","PeriodicalId":133667,"journal":{"name":"The Marsh Builders","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128261732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Emperor Joseph’s Roots","authors":"S. Levy","doi":"10.1093/oso/9780190246402.003.0008","DOIUrl":"https://doi.org/10.1093/oso/9780190246402.003.0008","url":null,"abstract":"On a May morning in 1957, ten thousand fish floated on the eastern edge of San Francisco Bay, their pale, upturned bellies bobbing on the surface of the dark water. The crowd of carcasses described an arc that stretched along the shore from Richmond’s harbor south to Point Isabel. Many striped bass, a prized game fish, were among the dead. Seth Gordon, director of California Department of Fish and Game (DFG), fielded complaints from anglers outraged by the fish kill. The Public Health Committee of the State Assembly passed a resolution admonishing DFG for its failure to enforce pollution control laws. Gordon told the committee members off. “We want to stop pollution,” he said, “but the law as it stands puts our Department in the position of a boxer going into the ring with one hand tied behind his back.” The ability to set and enforce pollution standards rested with California’s nine regional water pollution control boards. To effect any change, Gordon’s department had to prove to the boards’ satisfaction that pollution allowed by existing standards was harmful to fish, a challenge that had so far proved impossible. Responding to questions about the East Bay fish kill, he said, “We still don’t know what caused the die-off, or where it came from.” David Joseph was then starting out as a DFG biologist, armed with a doctorate in marine biology from the University of California at Los Angeles. Born in Connecticut, on a cooperative farm where his parents raised dairy cows and shade-grown tobacco with other immigrant Russian Jews, he’d grown up in Inglewood, in southern California, when the place was still a bucolic town and he could ride his horse to the beach. He’d met his wife, Marion, when they were both students at UCLA. “He was an outdoor guy,” she remembers. “He wasn’t a fisherman, he just loved the sea, loved the land. His work was always going to have something to do with protecting the environment.”","PeriodicalId":133667,"journal":{"name":"The Marsh Builders","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121275390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Fight This Time","authors":"S. Levy","doi":"10.1093/oso/9780190246402.003.0018","DOIUrl":"https://doi.org/10.1093/oso/9780190246402.003.0018","url":null,"abstract":"Forty- five years after the passage of the Clean Water Act (CWA), water pollution remains a profound problem. More than forty- seven thousand US waters are impaired. At the rate these lakes, rivers, and estuaries are being cleaned up, it will take more than five hundred years to make them all safe for swimming and fishing. Oliver Houck, a professor of law at Tulane University who has focused on environmental protection since the 1970s, sums up the situation: “We have not had clean water in America,” he writes, “in the lifetime of anyone living.” The major source of pollution in the waters of the US, as in other developed countries, is now runoff from farm fields and city streets. These nonpoint sources remain difficult to control. More than 75 percent of the rivers and lakes that fail to meet water quality standards are tainted by nonpoint sources. In terms of nutrient pollution, agricultural runoff is by far the dominant source, triggering harmful algal blooms from Chesapeake Bay to Puget Sound. The CWA of 1972 addressed point sources of pollution in a decisive and radical way. Section 402 of the CWA applies effluent standards based on the best available treatment technology to city sewage and industrial wastewaters, and puts regulatory power in the hands of the federal Environmental Protection Agency (EPA). Regulation under this scheme has brought dramatic improvement in water quality. Before the CWA was enacted, major urban river systems throughout the country had such low levels of dissolved oxygen that fish kills became routine, and urban beaches were often closed due to fecal contamination. By the late 1990s, dissolved oxygen levels had improved in about 70 percent of river reaches and watersheds studied by the EPA, and fish had returned to many waters. Beach closures decreased. Problems remain, especially in cities like Chicago and Baltimore, where heavy rains can overwhelm treatment systems, releasing raw sewage downstream. Still, in terms of curbing point source pollution, the CWA has made a critical difference. The rise of pollution from unregulated nonpoint sources has eaten away at these water quality gains. The Mississippi River basin, whose waters flow into the northern Gulf of Mexico, may be the most dramatic example. In August 2017, the Gulf’s dead zone grew to an unprecedented 8,776 square miles, about the size of New Jersey.","PeriodicalId":133667,"journal":{"name":"The Marsh Builders","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126600522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}